Escherichia coli was cultivated under hydrostatic pressures up to 30 MPa (300 bar) and then partitioned between an aqueous phase (physiological saline) and oil phase (n-hexadecane). The partition coefficients were used as measures of hydrophobicity of the surface of the cells and correlated with the susceptibility to an antimicrobial agent (dodecylpyridinium iodide). This agent is lethal to the cells and the effect of pressure on its concentration for a lethal effect on E. coli was determined. A good correlation was found between the hydrophobicity of the cells and their death rate on treatment with this reagent.